JAVA之IO技术-自定义的LineNumberReader类

package ioTest.io2;
/*
* 自定义一个带有读取行号方法的读取文件的装饰类
*/
import java.io.FileReader;
import java.io.IOException;
import java.io.Reader;

public class MyLineNumberReaderDemo {

public static void main(String[] args) throws IOException {
String line;
//创建输入流-读取文件信息到流中区，所以对于流来讲是“入”了
FileReader in=new FileReader("BufferedWriterDemo.java");
MyLineNumberReader mlnr=new MyLineNumberReader(in);
while((line=mlnr.MyReadLine())!=null)
{
System.out.println(mlnr.getLineNumber()+":"+line);
}
mlnr.close();
}

}
//定义一个自定义的类似于LineNumberReader的类
class  MyLineNumberReader extends Reader{
private Reader r;
int lineNumber;
int ch=0;
String line=null;
//根据构造函数判断，显然此类也是一个构造类
MyLineNumberReader(Reader r)
{
this.r=r;
}
public String MyReadLine() throws IOException {
lineNumber++;
StringBuilder sBuilder=new StringBuilder();
while((ch=r.read())!=-1)
{
if(ch=='\n')
continue;
if(ch=='\r')
return sBuilder.toString();
else
sBuilder.append((char)ch);
}
if(sBuilder.length()>0)
return sBuilder.toString();
return null;
}

public int getLineNumber() {
return lineNumber;
}
public void setLineNumber(int lineNumber) {
this.lineNumber = lineNumber;
}
@Override
public int read(char[] cbuf, int off, int len) throws IOException {
// TODO Auto-generated method stub
return 0;
}
@Override
public void close() throws IOException {
// TODO Auto-generated method stub
r.close();
}
}